1. Technical Field
The present invention concerns a board turner intended for use on a conveyor and in particular a board turner for use on conveyors carrying large volumes of boards.
2. Description of the Background Art
A number of devices for turning boards in timber processing machines are previously known. U.S. Pat. No. 5,482,140 describes a rotating board turner for use on a conveyor. The power used to turn the boards is achieved by the forward motion of the boards themselves while they are being transported along the conveyor. The device comprises a rotating hub with arms located at regular distances from each other in the same plane that extend radially out from the hub. Each and every one of the arms comprises a board holder for receiving the boards from the conveyor""s board transporter and retaining the boards while the arm rotates around the hub and laying the board back on the conveyor downstream from the turner. This device is located in direct connection with the transport path of the boards and turns all the boards.
U.S. Pat. No. 5,605,216 describes a board turning device for use on a conveyor for transporting boards through an inspection station. The boards are inspected with photocells that are connected to a computer for analyzing the result of the board inspection. To the computer is also connected a turning arm and in response to a signal from the computer, the turning arm is induced to engage an edge of the board and turn the same by rotating it around its opposite edge. This device rotates the board backwards and therefore requires a space behind each board corresponding to at least the width of the board itself.
U.S. Pat. No. 4,907,686 describes an electromagnetic system for reorienting the position of a sensed or detected article transported on the inclined surface of a conveyor. Plates transported on the conveyor are turned by means of a reciprocating thrower that forwards an impulse to one end of non-movable plate that induces the plate to turn over. This system requires space in front of the plate that is at least equal to the width of the plate itself. U.S. Pat. No. 4,936,437 describes also a board turning device comprising a plate exhibiting a support for stopping the board and a lifting surface. This turner throws the board in response to switches that are triggered either manually or by the board itself.
All the board turners described above are mounted in or below the conveyor for the boards being turned. The device described in U.S. Pat. No. 5,482,140 can turn the board within its own area on the conveyor without any need for additional space on any side of the board, which is necessary for this function in the other devices described in the patents. The device described in U.S. Pat. No. 5,482,140 turns every board on the conveyor, however. One object of the present invention is to achieve a board turner that makes it possible to increase the volume of processed boards while maintaining the possibility of allowing a board to pass without turning.
In agreement herewith is achieved a board turner intended for use on a conveyor for transporting boards where the conveyor defines a carrying plane for supporting the boards, whereby the board turner comprises means of rotation and means of gripping mounted on the means of rotation, where the means of gripping is arranged at a lateral distance from the conveyor and exhibiting a rotation path forming a carrying plane that is essentially parallel to the plane that is defined by the conveyor""s rotation path, whereby the rotation path of the means of gripping extends above and below the plane of the conveyor, the means of gripping has an open position and a closed position and is switchable between these positions as a response to a signal from a sensor in which in the open position the means of gripping rotates past the carrying plane without coming into contact with a synchronously arriving board and by which means with the help of a signal from the sensor the means of gripping is switched between the open position and the closed position while the means of gripping rotates upward in a straight line with the synchronously arriving board while gripping two opposite surfaces of a laterally extending part of the board, whereby the means of gripping continuously rotating above the conveyor in this way turns the board and returns the board to the conveyor in response to a second signal that switches the means of gripping from the closed position to the open position.
Principally, the means of rotation rotates so that the means of gripping is located in a synchronized line with every board while the means of gripping rotates upwards and past the carrying plane of the conveyor.
Principally, the rotation axis of the means of rotation is essentially parallel to the rotation axis of the conveyor when the means of rotation is used together with it.
The rotation axis of the means of rotation is suitably located below the carrying plane of the conveyor.
Principally, the means of gripping comprises a gripping unit that exhibits a pair of facing gripping parts designed to close against each other and open away from each other in response to a signal from a sensor allowing the gripping parts to grip and release boards being transported on the conveyor.
Principally, the means of gripping is controlled mechanically, electrically, pneumatically or hydraulically.
A cylinder is suitably used to operate the means of gripping in response to a signal from the sensor.
In a present embodiment, the means of gripping comprises two linking pieces that together with their respective ends are hinge-mounted to a piston rod and which each individually at their respective other end is connected to a one of the facing gripping parts, a support part combined with each of the said link pieces and hinge-mounted at one end located between the link piece ends and hinge-mounted at the other end to a construction that is immovable relative to the link pieces and the cylinder, by which means the operation of the piston affects each link piece to swing around a hinge point between the ends of the same and in doing so move the facing gripping parts away from each other or towards each other.
In one embodiment, the turner is a separate unit located at a lateral distance from the conveyor.
Principally, there is a separate means of driving arranged for rotation of the means of rotation.
The means of rotation is suitably connected to a means of driving the conveyor.
Principally, the coupling between the means of rotation and the means of driving the conveyor achieves a synchronized alignment between the means of gripping and each board.
Principally, the coupling is a mechanical coupling arranged by means of a chain that links the two drive wheels to each other, of which one wheel is mounted on the means of driving the conveyor and the other wheel is mounted on the means of rotation.
In another embodiment, the synchronized alignment between the means of gripping and the board is achieved electronically.
The invention further comprises a conveyor with a board turner arranged on it.
Principally, the means of rotation is arranged with a rotation unit comprising a continuous shaft that is mounted in a protective sleeve located along the conveyor.
In operation, the conveyor transports the boards with their longitudinal axes extending across the direction of the conveyor and the means of rotation rotates the means of gripping, whereby the means of gripping is in synchronous alignment with each board while the means of gripping rotates upwards from a position below the carrying plane of the conveyor, a sensor detects the boards and as a response to the event that a board is to be turned, the sensor sends a signal to the means of operating the means of gripping, whereby the means of gripping is switched from an open position to a closed position by means of an upper means of control and at the moment of alignment, the means of gripping grips one end of the board extending sideways from the conveyor, the means of gripping continues to rotate above the carrying plane of the conveyor and the board is turned, the means of gripping is activated between its closed position and open position in response to a second signal allowing the means of gripping to release the end of the board for returning it to the conveyor.
Principally, the board is replaced in its original position on the conveyor.
Principally, three means of gripping are mounted on the means of rotation, which seen from the direction of rotation are located at equal distances from each other around the axis of the means of rotation.
The gripping surfaces of the gripping parts should be essentially parallel with the surfaces of the board to be gripped while the means of gripping rotates in line with the synchronously arriving boards.
Principally, a photoelectric sensor is used to monitor the boards and generate a signal that is conveyed to the means of controlling the means of gripping when the sensor determines that a board is to be turned.
Around two hundred boards per minute can suitably be turned.